1. Field of the Invention
The present invention relates, in general, to billiard cues and, more specifically, to billiard cue shafts.
2. Description of the Art
Billiard or pool cues typically are formed of an elongated shaft; a butt at one end of the shaft and a ferrule mounted at an opposite end which supports a tip. The shaft may be formed as a solid, one-piece member or of two threadingly engageable sections. Typically, the shaft has been formed of a hard wood, such as a hard maple.
Other materials, such as aluminum, steel, plastic and carbon fiber, have also used to form billiard/pool cue shafts. Cues formed of such “non-wood” materials have been engineered to approximate wood in weight and stiffness or rigidity; however none have proven to play better than a hard wood cue.
It is also known to form cue shafts of solid maple with a thin composite outer skin formed of various fibers and/or resin combinations. It is known to form a cue shaft of a solid glass bonded fiber as shown in U.S. Pat. No. 3,103,359. It is also known to form a cue shaft as a composite tube of carbon fibers in which the shaft has a wall thickness of 0.060 inches or more and the hollow interior of the shaft is filled with foam as shown in U.S. Pat. No. 4,816,203. U.S. Pat. No. 5,112,046 discloses a shaft formed of a solid epoxy resin body with a central graphite core. This shaft accommodates flexure and impact by utilizing elongated carbon filaments circumferentially spaced apart and concentrically disposed about the core and extending axially through the front and rear sections of the shaft.
Generally a billiard or pool cue is formed with one of two styles of taper. In an “American” taper, the cue has a constant diameter of approximately 0.5 inches for approximately the first twelve inches from the tip end, this being the longest bridge length commonly used in play. The other common type of taper is a so-called “European taper”. In this style of cue, the cue has a truncated cone shape along its entire length tapering to a tip.
Previously devised ferrules have been formed of ivory which is substantially harder than that of the material used to form the shaft. More recently, reinforced phenolics and thermoplastics have been employed to form ferrules. Such ferrules have a modulus of elasticity ranging from a high of 1.3×106 psi to a low of 0.35×106 psi as compared to the 1.8×106 psi modulus of elasticity of hard maple commonly used to form the shaft. The ferrule is adhesively joined to and/or press fit to one end of the shaft, typically by means of a tenon in the form of a narrow diameter end portion which projects out of the end of the shaft into a hollow bore extending inward from one end of the ferrule or, alternately, from the ferrule into a bore in one end of the shaft. The tip, which is typically formed of leather, is adhesively joined to the ferrule.
In use, the shaft is lined up with the intended path of movement of the cue ball prior to stroking the shaft to impact the tip on the ball. The cue can also be lined up to strike the cue ball off center, that is, to the left or right of the center of the ball, or above or below the center of the ball, to generate spin, draw or follow to the cue ball to cause it to move in a desired direction after it strikes another ball or a rail. However, as a result of a hit to the left or right of center, the cue ball does not follow a path of movement that is parallel to the line of stroke of the cue. Rather, the cue ball deflects or moves in a path at an angle to the line of stroke of the cue. This so-called angle of deflection varies with the speed of the stroke and how far from center the cue tip strikes the cue ball, but with a given off center distance and speed, the magnitude of the angle of deflection is primarily a function of the cue itself
During off center hits, the tip, ferrule and the end of the shaft up to the player's hand bridge initially buckles due to loading of the impact forces generated during impact of the tip with cue ball on an inside edge of the shaft closest to the center of the ball. This buckling is then followed by an outward flexing of the tip, ferrule and shaft end. Experimentation by the Applicants has shown that a large amount of buckling results in a larger and more undesirable deflection of the cue ball from a path of movement parallel to the cue stroke line than when buckling is minimized and the end of the cue more easily flexes or bends outward from the center of the cue ball after impact with the cue ball. Applicants have also found that a substantial amount of the cue ball deflection is due to the mass or weight of the shaft at the tip end of the shaft.
In order to address the cue ball deflection problem, the Applicants devised a billiard/pool cue disclosed in U.S. Pat. No. 5,725,437 and in co-pending application, Ser. No. 08/825,247. In both of these disclosures, a hollow bore is formed in the shaft extending from the first end for a predetermined distance toward the second or butt end. The bore forms a hollow cavity in the shaft after the ferrule is mounted on the first end of the shaft. The purpose of the bore is to reduce the weight of the tip end thereby resulting in a lighter tip end which is capable of easier outward flexing than previously devices cue shafts since the tip end can quickly accelerate laterally due to its reduced weight. The shaft of the cue disclosed in this patent and pending application is made of wood thereby necessitating large wall thicknesses for strength.
To further reduce the wall thickness of these prior cues devised by the applicants, the Applicants made refinements disclosed in co-pending application Ser. No. 09/200,244, mentioned above. In this disclosure, the Applicants devised a billiard cue having a shaft formed with the hollow bore extending from a first end and having a wall thickness of about 0.030 to about 0.050 inches. The shaft was preferably formed of fibers disposed in a binder, such as carbon fibers disposed in an expoxy resin binder. A shaft wall construction of this type typically has a modulus of elasticity of greater than 4.3×N 106 P.S.I. for a 0.5 inch O.D. tip and shaft in the above described wall thickness of about 0.03 inches to about 0.05 inches.
Thus, the tip end of the shaft had significantly reduced weight as compared to the applicant's previously devised wood shaft with a hollow bore at the tip end while still retaining a high degree of rigidity to produce the desired significant reduction in buckling of the cue tip upon impact with a ball.
While billiard cues were constructed by the Applicants in either the wood or fiber versions as described above with a hollow bore extending for a predetermined distance from the tip end, thereby producing the shaft with greater deflection upon impact with a cue ball without buckling, it is believed that further improvements with respect to additional reductions in tip end weight can be obtained without sacrificing the requisite stiffness to weight ratio of the billiard cue.
Thus, it would be desirable to provide a billiard cue which has a significantly reduced weight at the tip end of the shaft while maintaining sufficient stiffness to minimize flexure or buckling of the tip end of the shaft and thereby deflection of a ball struck by the cue. It would also be desirable to provide a billiard cue formed of a material having high strength and stiffness; while at the same time providing a light weight and low mass at least at the tip end of the shaft. It would also be desirable to provide a billiard cue formed of a material having a unique combination of stiffness and lightweight to enable the tip of the cue to be displaced on impact with a ball while still remaining in contact with the ball as the ball begins to rotate.